1. Field of the Invention
The invention relates to a process and device for dispersing fibrous paper material.
2. Discussion of Background
Processes for dispersing fibrous paper material are, for example, necessary for the improvement of the quality of fibrous material, which is extracted from used paper. It is known that fibrous paper material can be homogenized and thereby significantly improved through dispersion. In many cases a fibrous material is used, which exhibits a dry content between about 15% and 35% and which has been brought to a temperature which is significantly above the ambient temperature. It is prudent to undertake the calefaction, i.e., warming, if the fibrous material already has the consistency necessary for dispersion. With this thickening process, a considerable portion of the water, which was previously still present in the fibrous material, is removed before calefaction. Through this process, first, its viscosity increases significantly in the dispersion and second, less water must be calefied. The most important machines for the thickening are worm presses and sieve presses.
With a sieve press, the fibrous material suspension is fed in between a sieve and a roll or between two sieves and pressed, so that the water is discharged. As a result, a moist fibrous material web is formed. Depending upon the operational parameters, this web has a solid matter G.S.M. between about 500 g/m.sup.2 and 2000 g/m.sup.2. Pressures which deviate from this range, however, can also be advantageous. The moist web is taken from the area of the sieve or the sieves and must, thereafter, be torn into flat pieces. These pieces are easy to calefy to the desired temperature, but a relatively long calefaction period is necessary. Thus, calefaction periods of, for example, several minutes must be accepted, especially if a temperature above 90.degree. C. is desired. Thereafter, the hot, friable material is fed into a disperser. The entire process requires a device that is quite expensive.
With a worm press, the fibrous material suspension is pressed between a worm conveyer and a perforated jacket surrounding it, whereby the water leaves through the jacket. The resulting pressed pulp, or plug, is pressed from the worm and breaks into pieces. Only a relatively long calefaction period can bring these pieces to the desired temperature. A further pulverization can, for example, occur in a pulverizing worm or in a system with counter-rotating rotors, which is, however, very expensive.